8 + y = 8 – y

$y=0$    is the answer

Let's look at the original equation:
 

$8+y=8-y$

To solve this, we must isolate y. This means that we need to get the equation into y equals form. 

$8+y=8-y$ Subtract 8 on both sides

If you subtract a number on one side of the equation, you must do that on the other, of course. When you subtract 8 on both sides, you are left with:

$y=-y$     Add y to both sides

$y+y=0$     Combine like terms

$2y=0$     Divide by 2 to isolate y

$y=0$

If you are ever unsure whether an answer is correct or not, plug the value you got back in the original equation:

$8+0=8-0$

$8=8$

This statement is true, so y=0 is the correct and the only correct value for y.